The conformational studies of steroid binding enzymes will be undertaken by ultraviolet, spectro polarimetric, and spectro fluorescent spectral difference methods. Towards this end the synthesis of the new affinity labeling steroids will be completed, and formerly prepared steroids will be evaluated for use in the conformational studies. Simultaneously, "working" quantities of sheep and/or calf uterine progesterone and estrogen receptor proteins will be isolated with the "disulfide" affinity chromatography columns, characterized and evaluated for storage life-time. If the purified receptor proteins are found to be stable then a "stock pile" will be built up. However, if the pure receptor proteins turn out to be unstable on storage, then quantity preparations will await the third year of this research project. By this time the ground work for physico-chemical studies of the conformation of these proteins will have been layed by the coming years' work with model proteins.